1. Field of the Invention
The present invention relates to a memory controller, a memory control method, and a memory control system. The invention may be preferably used, for example, in volatile memory refresh control.
2. Description of Related Art
Volatile memory including DRAM (Dynamic Random Access Memory) has a memory cell structure to hold data, and the memory has to be periodically refreshed. Refresh control of the volatile memory is performed by a memory controller connected to the memory. The volatile memory and the memory controller are embedded in a system requiring a volatile memory, and operate based on a clock generated within the system. In particular, the memory controller performs volatile memory control including refresh control based on a system clock generated within the system or a clock obtained by frequency dividing the system clock.
Meanwhile, a refresh control specification as stipulated for a volatile memory is prescribed as a “requirement to issue a refresh command at least a certain number of times within a certain period”. That is, it is sufficient if the memory controller is in compliance with the specification concerning refresh control of the volatile memory, and timing at which a refresh command is issued is left to the memory controller.
In this regard, Patent Literature 1 discloses technology implemented by proceeding with refresh control for a volatile memory when the memory controller is in an idle state. By the memory controller disclosed in Patent Literature 1 being implemented to proceed with refresh control, it is not necessary to give priority to refresh control when the memory controller is in a busy state, and deteriorated performance of the overall system including the volatile memory is prevented.
In addition, Patent Literatures 2 to 7 disclose various types of technology concerning refresh control of volatile memory, and Patent Literatures 8 to 9 disclose technology where refresh control of volatile memory is realized.
[Patent Literature 1]
    JP Patent Kokai Publication No. JP2011-018435A[Patent Literature 2]    JP Patent Kokai Publication No. JP2000-235789A[Patent Literature 3]    JP Patent Kokai Publication No. JP2003-151270A[Patent Literature 4]    JP Patent Kokai Publication No. JP2009-059412A[Patent Literature 5]    JP Patent Kokai Publication No. JP-H04-060988A[Patent Literature 6]    JP Patent Kokai Publication No. JP-H06-236683A[Patent Literature 7]    JP Patent Kokai Publication No. JP-H08-129883A[Patent Literature 8]    JP Patent Kokai Publication No. JP2007-287314A[Patent Literature 9]    JP Patent Kokai Publication No. JP2010-170608A